feat: better unwrapping of java exception

pkg/codec.go

@@ -22,6 +22,7 @@ package dubbo
 import (
 	"context"
 	"fmt"
+	hessian2_exception "github.com/kitex-contrib/codec-dubbo/pkg/hessian2/exception"
 
 	"github.com/kitex-contrib/codec-dubbo/registries"
 
@@ -182,12 +183,12 @@ func (m *DubboCodec) encodeExceptionPayload(ctx context.Context, message remote.
 	if !ok {
 		return nil, fmt.Errorf("%v exception does not implement Error", data)
 	}
-	if exception, ok := data.(hessian2.Throwabler); ok {
+	if exception, ok := data.(hessian2_exception.Throwabler); ok {
 		if err := encoder.Encode(exception); err != nil {
 			return nil, err
 		}
 	} else {
-		if err := encoder.Encode(hessian2.NewException(errRaw.Error())); err != nil {
+		if err := encoder.Encode(hessian2_exception.NewException(errRaw.Error())); err != nil {
 			return nil, err
 		}
 	}

pkg/hessian2/exception.go → pkg/hessian2/exception/exception.go

@@ -17,9 +17,12 @@
  * limitations under the License.
  */
 
-package hessian2
+package exception
 
-import "github.com/apache/dubbo-go-hessian2/java_exception"
+import (
+	"github.com/apache/dubbo-go-hessian2/java_exception"
+	"github.com/cloudwego/kitex/pkg/kerrors"
+)
 
 type Throwabler interface {
 	java_exception.Throwabler
@@ -28,3 +31,26 @@ type Throwabler interface {
 func NewException(detailMessage string) Throwabler {
 	return java_exception.NewException(detailMessage)
 }
+
+// FromError extracts Throwabler from passed err.
+//
+//   - If err is nil, it returns nil and false
+//
+//   - If err is of type *kerrors.DetailedError, it would unwrap err to get the
+//     real cause. Then it would check cause whether implementing Throwabler. If
+//     yes, it returns Throwabler and true.
+//
+//     If not, it checks err whether implementing Throwabler directly. If yes,
+//     it returns Throwabler and true.
+func FromError(err error) (Throwabler, bool) {
+	if err == nil {
+		return nil, false
+	}
+	if detailedErr, ok := err.(*kerrors.DetailedError); ok {
+		err = detailedErr.Unwrap()
+	}
+	if exception, ok := err.(Throwabler); ok {
+		return exception, true
+	}
+	return nil, false
+}

pkg/hessian2/exception/exception_test.go

@@ -0,0 +1,68 @@
+/*
+ * Copyright 2023 CloudWeGo Authors
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package exception
+
+import (
+	"github.com/cloudwego/kitex/pkg/kerrors"
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func TestFromError(t *testing.T) {
+	tests := []struct {
+		desc     string
+		inputErr error
+		expected func(t *testing.T, exception Throwabler, ok bool)
+	}{
+		{
+			desc:     "nil err",
+			inputErr: nil,
+			expected: func(t *testing.T, exception Throwabler, ok bool) {
+				assert.Nil(t, exception)
+				assert.False(t, ok)
+			},
+		},
+		{
+			desc:     "Throwabler err",
+			inputErr: NewException("FromError test"),
+			expected: func(t *testing.T, exception Throwabler, ok bool) {
+				assert.Equal(t, "java.lang.Exception", exception.JavaClassName())
+				assert.Equal(t, "FromError test", exception.Error())
+				assert.True(t, ok)
+			},
+		},
+		{
+			desc:     "DetailedError wraps Throwabler",
+			inputErr: kerrors.ErrRemoteOrNetwork.WithCause(NewException("FromError test")),
+			expected: func(t *testing.T, exception Throwabler, ok bool) {
+				assert.Equal(t, "java.lang.Exception", exception.JavaClassName())
+				assert.Equal(t, "FromError test", exception.Error())
+				assert.True(t, ok)
+			},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.desc, func(t *testing.T) {
+			exception, ok := FromError(test.inputErr)
+			test.expected(t, exception, ok)
+		})
+	}
+}